Apparatus for the measurement of fluids.



- A. NI. LEVIN.

APPARATUS` FOR THE MEASUREMENT oF mums. APPLICATION FILED APR. I3, 1914.

LIIAQU.

Patented May 2,1916.

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RVID M. LEVIN, .0F CHICAGO, ILLINOIS.

APPARATUS FOR THE MEASUREMENT OF FLUIDS.

i To all whom t may concern:

'Be it'known .that I, Anvn) M. Lnvirna citizen of the United States,residing at Chicago, in the county of lCook and State of Illinois,haveinvented-v a new and useful Apparatus for the Measurement of Fluids,of which the following is a specification. 4

The invention relates to that class of measuring apparatus usedparticularly for the measurement of the velocity of flow of liquids orgases in closed-channels. In the generally employed flow measuringinstruments of this class, the determination of the velocity ofow isbased on the established change in the pressure of the fluid that willresult from a certain definite change in its velocity, With respect toincompressible such as water, the generally employed instruments, the'Pitot tube and Venturi meter, have proven satisfactory and reliable;

4lout with respect to compressible fluids, such asfsteam, air or gasesgenerally they lack in accuracy, on the ground that theinertia pressurevaries throughout a given section of the conduit, not only because ofVariations in the velocity due to ordinary frictional resistancesbutalso because of eddies and whirls in the fluid itself;

With the present invention, 'which is particularly intended'for themeasurement of comcpressi'ble fluids, in' which there can expected toexist an even approximately uniform current,.it is contemplated toestablish the centrifugal pressure that must be due to a certaindefinite change in the direction of motion'of the fluid, and to use thiscentrifugal pressure as a basis for the determination of the velocity orvolume of `flow. This object .is ra-tus illustrated in Figures 1 and 2of the attained by the appa accompanying drawing, of which- Fig. 1 is alongitudinal section through the connection with pressure indicatinginstruments shown in elevation;- Fig. 2is a cross section on the line AA of Fig. 1.

'y Fig. 3 is a diagrammatical illustration showing how the forces actupon the fluid passlng through the apparatus and it is submitted for thepurpose of serving as a key Specification of Letters Patent.

ly, without exceptional precautions, be i Patented May a, raie.

Application filed April 13, 1914. Serial No. 831,684.

to the deduction of certain necessary formulas which will be given inthe following. Similar figures refer to similar parts throughout theseveral views.`

The apparatus consists essentially of an elbow or bend 1 Fig. l, whichmay be any shape in cross section, shown respectively by Fig. 2 and Fig.3.

2 and 3 are nozzle-plugs extending through respectively the outer andthe inner curved wall of the bend and conforming at their inwardextremity with the curvature ofthe bend so as to form a smooth channelthroughout the sweep of the bend.

4 are pressure ports extending from the outer curved wall of the bendand communicating with a common pressure chamber 6, while 5 are pressureports extending Yfrom the .inner curved wall of the bend andcommunicating with a common pressure cham ber 7 The pressure chambers 6and 7 terminate in the pipe connections 8 and 9.

10 is a. Uetube manometer, and 11, 12 and 13 are pipes connecting theterminals of the U-tube with the pressure chambers 6 and 16 is u plugcock which has for its object to enable the operator to throttle theliquid in the U-tube sulliciently to make it perfectly steady whenreading the instrument.

In employing the apparatus, it is inserted as an elementary part of thechannel which conducts the fluid to bemeasured, and the pressurechambers 6 and 7. are connected toV any Suitable pressure readinginstrument for determining the pressures created in these chambers, asfor instance with the manometer 10 shown in the illustration. It will beevident that, as the fluid passes through the bend, a certaincentrifugal force mustbe exerted in changing the course of the fluid.The value of this centrifugal force will be quite definite, depending onthe velocity with which the fluid passes, and it will cause the pressureat the outer pres sure-ports, 4, to increase while the pressure at theinner pressure ports, 5, decreases. The new pressures thus obtained atthe pressureports will also vary with the velocity of the fluid, andthey will bey essentiall. independent of any irregularities o r whir sinside the ybody of the luidj- This will be understood when the fact isconsidered1 that it takes ex- 'actlythe same force to change thelinearlcourse of a whirling mass as that required to vchange the 'courseof the same mass oW- ing smoothly. Generally there will of course obtainin the fluid pulsations andwaves 4different points over a comparativelylarge ypart of the wall surface intoa mean pres-4 common pressurechamber.

Whichbecome transmitted directly to the. .Walls of the How bend, andwhich thus would variously afect the centrifugal pres-A -suresestablished at individual points of the Wall surface. v`For that reason,in orderto average up the slightly varying pressures at serve very"correctly, if carefully measured,

as a gage for the velocity of flow. For the 'reduction of the pressuresregistered by the indicating instruments into velocity of flow, certainformulas will be required. These formulas are quite simple, and may bede duced as follows z-Let Fig. represent a cross section normal t'o theaxisof the low bend, such as a. section through line D.D of Fig.'1, O Obeingan axis through the center of curvature of the bend; and let mrepresent an elementary mass-of the -iiuid passing through; .Thesectional area of m, normal to the radius of, the bend, is a and its'length dm.' In turning the bend, the mass m Willbe acted upon by acertain centrifugal `forc C,causing.it to compress'the iiuid ra diallyin front of it from a pressure p to a pressure p-l-dp. The increase inpressure on the area f must manifestly at all instants balancethecentrifugal force C; hence We 'have l5oY ' and substituting mainsunchanged. during the fio'w,

whenI g is lthe acceleration dueto gravity, we get the general equationp y assumptions may be made :-1, that it reas 1n the casewith respect towater; 2,tl1`atit.ohanges according to th'e laws of. isothermalcornpression as in the case of a saturated vapor;

3, that it changes according to the laws of adiabatic compression as inthecase of a permanent' gas.

Assuming-'(1) 8 to be `a consta-nt quantity,

then We obtain from' the general. equation (1)' and through integrationi But, as vand Z? are pressure-heads eX- essed infeet head of the Huidcorrespond* 1n to the pressures p2 and p, We may Write Let be the meanlinear velocity of the uid showing through the bend. ThusA Y awarded@Finally; call R r.= D the, diameter o# width of the channel, @in vgl@ERS-?thev mean radius of the'bend;` A'and vire get Vmz l y i i 2 9--PUL' i714) which may be vvyritten. i

When'v/'r-` (ly-h1) is the. difference in pressure-head at the outerand' inner iwall of the bend.

ilowing through the' bend Vto' change according to the laws ofisothermal compression,

' .The correspondingequation-for thewell a known Pitot tube is Withrespect' to the density of the fluid,

' -r the quantity, 8 in the above equation', three '125l then thegeneral grated into equation (l) may be inte- Finally, assuming (3) thedensity of the Huid to change according to the laws of adiabaticcompression, then' eguation (l) becomes after integration and thecorresponding equation for the Pitot tube is A comparison between eachset of equationsv will show that the formula for the velocity of flowthrough the flow-bend is, in each case, exactly the same as thecorresponding formula for the Pitot tube, with the factor adjoined. Thiswill of course also be the case with respect to the formulas 'for volumeof flow and Weight of flow. In other Words, the pressure-head, l1.,indicated by the Amanometer tube will for the same velocity in the caseof the flow-bend be 212 of the pressure head indicated by the Pitottube. The quantity may ordinarily be '1% to 2, and hence, the 'pressurehead indicated by the flow bend will for the same velocity be vone and ahalf to twice the head indicated yby the .Pitot tube. ,This will ofcourse with respect to small velocities be i a feature of considerableadvantage in favor -Having thus Adescribed my invention, what I claimis 1. In a flow measuring apparatus, a curved channel or flow bendprovided with a plurality of pressure ports arranged in acircumferential line in its inner androuter Icurved walls and I neansfor determining the difference betweeny the pressure obtaining in l`theports in the outer curved wall and that a plurality of pressure ports inits outer and y inner curved walls arranged in a circumferential line,means connecting all the ports in the outer wall, means connecting allthe ports in the inner wall and means for deter-u mining the differencebetween the pressure obtaining in said first named means and thepressure obtaining in the second named means. v y

3. In a flow measuring apparatus, a curvedV channel or How-bend providedwith a plurality of radial pressure ports spacedA successively in acircumferential line along its outer curved wall and with a plurality ofradial pressure ports spaced successively in a I,circumferential linealong its inner curved wall, and means for 'determining the differencebetween the mean pressure obtaining -in the ports in the outer curvedWall and the mean pressure obtaining in the ports in' the inner curvedwall when a Huid isl passed through the flow-bend.

4. In a ow measuring apparatus a curved channel or flow-bend providedWitha plurality of radial pressure ports spaced- 'curved channel orflow-bend, a removable nozzle plug comprising a pressure chamber and aplurality of pressure ports arranged in a circumferential line whichcommunicate with the channel or flow-bend and the pressure chamber saidvnozzle vplug extending through the outer curved wall of the curvedchannel or flow-bend, a second removable nozzle plug comprising apressurechamber and a plurality of pressure ports arranged in acircumferentialV line communicating with the channel or How-bend andthepressure chamber, said second named plug eX- tending through the innercurved Wall of the curved channel orf1ow-b'end'an means for measuringthe pressure differenqe existing between said pressure chambers when 'afluid is passed through the curved channel or flow-bend.

6. In a iow measuring apparatus, a curved channel o1' flow-bend of adefinite cross sectional area and radius of curvature,

a nozzle plug comprising a pressure chamber and a plurality ofpressure'ports ar-- ranged in a circumferential line communicatlng withthe pressure chamber and having its inner extremity conforming to thegeneral conformation of the. channel or How-bend, said plug extendingthrough the outer curved `ulall of the channel 'or {iowbend, a secondnozzle plug comprising a .pressure chamber and a plurality lofpressureports arranged in a circumferential line communlcatmg with the pressurechamber and having its inner extremity conforming to the generalconformation of thechennel or flow-bend, said second plug extendingthrough the inner ,curved-,Wallof the chamber or flow-bend and means formeasuring the difference in the pressures existing in said pressurechambers -vilhen la uid is .passed through the curved channel or'ow; I

